How do you download a blender addon
Is seems that you accidentaly found a bug report on the addon you want to download. There is no download button. To browse available addons go to the Scripts Catalog. In case of the sapling addon it wouldn't be neccesary (see @cegaton's answer).

On the addon's page you find a download link:



For installation see:


http://wiki.blender.org/index.php/Doc:2.6/Manual/Extensions/Python/Add-Ons
Installing an addon